/*
** $Id: lbitlib.c,v 1.30 2015/11/11 19:08:09 roberto Exp $
** Standard library for bitwise operations
** See Copyright Notice in lua.h
*/

#define lbitlib_c
#define LUA_LIB

#include "lprefix.h"


#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"


#if defined(LUA_COMPAT_BITLIB)      /* { */


#define pushunsigned(L,n)   lua_pushinteger(L, (lua_Integer)(n))
#define checkunsigned(L,i)  ((lua_Unsigned)luaL_checkinteger(L,i))


/* number of bits to consider in a number */
#if !defined(LUA_NBITS)
#define LUA_NBITS   32
#endif


/*
** a lua_Unsigned with its first LUA_NBITS bits equal to 1. (Shift must
** be made in two parts to avoid problems when LUA_NBITS is equal to the
** number of bits in a lua_Unsigned.)
*/
#define ALLONES     (~(((~(lua_Unsigned)0) << (LUA_NBITS - 1)) << 1))


/* macro to trim extra bits */
#define trim(x)     ((x) & ALLONES)


/* builds a number with 'n' ones (1 <= n <= LUA_NBITS) */
#define mask(n)     (~((ALLONES << 1) << ((n) - 1)))



static lua_Unsigned andaux(lua_State *L)
{
    int i, n = lua_gettop(L);
    lua_Unsigned r = ~(lua_Unsigned)0;
    for (i = 1; i <= n; i++)
        r &= checkunsigned(L, i);
    return trim(r);
}


static int b_and(lua_State *L)
{
    lua_Unsigned r = andaux(L);
    pushunsigned(L, r);
    return 1;
}


static int b_test(lua_State *L)
{
    lua_Unsigned r = andaux(L);
    lua_pushboolean(L, r != 0);
    return 1;
}


static int b_or(lua_State *L)
{
    int i, n = lua_gettop(L);
    lua_Unsigned r = 0;
    for (i = 1; i <= n; i++)
        r |= checkunsigned(L, i);
    pushunsigned(L, trim(r));
    return 1;
}


static int b_xor(lua_State *L)
{
    int i, n = lua_gettop(L);
    lua_Unsigned r = 0;
    for (i = 1; i <= n; i++)
        r ^= checkunsigned(L, i);
    pushunsigned(L, trim(r));
    return 1;
}


static int b_not(lua_State *L)
{
    lua_Unsigned r = ~checkunsigned(L, 1);
    pushunsigned(L, trim(r));
    return 1;
}


static int b_shift(lua_State *L, lua_Unsigned r, lua_Integer i)
{
    if (i < 0)    /* shift right? */
    {
        i = -i;
        r = trim(r);
        if (i >= LUA_NBITS) r = 0;
        else r >>= i;
    }
    else    /* shift left */
    {
        if (i >= LUA_NBITS) r = 0;
        else r <<= i;
        r = trim(r);
    }
    pushunsigned(L, r);
    return 1;
}


static int b_lshift(lua_State *L)
{
    return b_shift(L, checkunsigned(L, 1), luaL_checkinteger(L, 2));
}


static int b_rshift(lua_State *L)
{
    return b_shift(L, checkunsigned(L, 1), -luaL_checkinteger(L, 2));
}


static int b_arshift(lua_State *L)
{
    lua_Unsigned r = checkunsigned(L, 1);
    lua_Integer i = luaL_checkinteger(L, 2);
    if (i < 0 || !(r & ((lua_Unsigned)1 << (LUA_NBITS - 1))))
        return b_shift(L, r, -i);
    else    /* arithmetic shift for 'negative' number */
    {
        if (i >= LUA_NBITS) r = ALLONES;
        else
            r = trim((r >> i) | ~(trim(~(lua_Unsigned)0) >> i));  /* add signal bit */
        pushunsigned(L, r);
        return 1;
    }
}


static int b_rot(lua_State *L, lua_Integer d)
{
    lua_Unsigned r = checkunsigned(L, 1);
    int i = d & (LUA_NBITS - 1);  /* i = d % NBITS */
    r = trim(r);
    if (i != 0)  /* avoid undefined shift of LUA_NBITS when i == 0 */
        r = (r << i) | (r >> (LUA_NBITS - i));
    pushunsigned(L, trim(r));
    return 1;
}


static int b_lrot(lua_State *L)
{
    return b_rot(L, luaL_checkinteger(L, 2));
}


static int b_rrot(lua_State *L)
{
    return b_rot(L, -luaL_checkinteger(L, 2));
}


/*
** get field and width arguments for field-manipulation functions,
** checking whether they are valid.
** ('luaL_error' called without 'return' to avoid later warnings about
** 'width' being used uninitialized.)
*/
static int fieldargs(lua_State *L, int farg, int *width)
{
    lua_Integer f = luaL_checkinteger(L, farg);
    lua_Integer w = luaL_optinteger(L, farg + 1, 1);
    luaL_argcheck(L, 0 <= f, farg, "field cannot be negative");
    luaL_argcheck(L, 0 < w, farg + 1, "width must be positive");
    if (f + w > LUA_NBITS)
        luaL_error(L, "trying to access non-existent bits");
    *width = (int)w;
    return (int)f;
}


static int b_extract(lua_State *L)
{
    int w;
    lua_Unsigned r = trim(checkunsigned(L, 1));
    int f = fieldargs(L, 2, &w);
    r = (r >> f) & mask(w);
    pushunsigned(L, r);
    return 1;
}


static int b_replace(lua_State *L)
{
    int w;
    lua_Unsigned r = trim(checkunsigned(L, 1));
    lua_Unsigned v = trim(checkunsigned(L, 2));
    int f = fieldargs(L, 3, &w);
    lua_Unsigned m = mask(w);
    r = (r & ~(m << f)) | ((v & m) << f);
    pushunsigned(L, r);
    return 1;
}


static const luaL_Reg bitlib[] =
{
    {"arshift", b_arshift},
    {"band", b_and},
    {"bnot", b_not},
    {"bor", b_or},
    {"bxor", b_xor},
    {"btest", b_test},
    {"extract", b_extract},
    {"lrotate", b_lrot},
    {"lshift", b_lshift},
    {"replace", b_replace},
    {"rrotate", b_rrot},
    {"rshift", b_rshift},
    {NULL, NULL}
};



LUAMOD_API int luaopen_bit32(lua_State *L)
{
    luaL_newlib(L, bitlib);
    return 1;
}


#else                   /* }{ */


LUAMOD_API int luaopen_bit32(lua_State *L)
{
    return luaL_error(L, "library 'bit32' has been deprecated");
}

#endif                  /* } */
